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WO2006061745A2 - Unite de detection optique concue pour etre utilisee dans un lecteur optique pour disques multiples et procede de correction des aberrations optiques dans une telle unite de detection optique - Google Patents

Unite de detection optique concue pour etre utilisee dans un lecteur optique pour disques multiples et procede de correction des aberrations optiques dans une telle unite de detection optique Download PDF

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Publication number
WO2006061745A2
WO2006061745A2 PCT/IB2005/054000 IB2005054000W WO2006061745A2 WO 2006061745 A2 WO2006061745 A2 WO 2006061745A2 IB 2005054000 W IB2005054000 W IB 2005054000W WO 2006061745 A2 WO2006061745 A2 WO 2006061745A2
Authority
WO
WIPO (PCT)
Prior art keywords
optical
radiation beam
pick
unit
record carriers
Prior art date
Application number
PCT/IB2005/054000
Other languages
English (en)
Other versions
WO2006061745A3 (fr
Inventor
Petrus T. Jutte
Joris J. Vrehen
Original Assignee
Arima Devices Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Arima Devices Corporation filed Critical Arima Devices Corporation
Priority to DE112005003102T priority Critical patent/DE112005003102T5/de
Priority to US11/792,275 priority patent/US20080259770A1/en
Publication of WO2006061745A2 publication Critical patent/WO2006061745A2/fr
Publication of WO2006061745A3 publication Critical patent/WO2006061745A3/fr

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Classifications

    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1392—Means for controlling the beam wavefront, e.g. for correction of aberration
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
    • G11B7/085—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam into, or out of, its operative position or across tracks, otherwise than during the transducing operation, e.g. for adjustment or preliminary positioning or track change or selection
    • G11B7/0857—Arrangements for mechanically moving the whole head
    • G11B7/08582—Sled-type positioners
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1392—Means for controlling the beam wavefront, e.g. for correction of aberration
    • G11B7/13925—Means for controlling the beam wavefront, e.g. for correction of aberration active, e.g. controlled by electrical or mechanical means

Definitions

  • Optical pick-up unit for use in a multi-disc optical player and method for correcting optical aberrations in such an optical pick-up unit
  • the present invention concerns to an optical pick-up unit for use in a multi- disc system according to the preamble of claim 1, an optical player according to the preamble of claim 13 and a method according to the preamble of claim 14.
  • An optical pick-up unit is the key component of an optical storage system called optical player, comprising a drive unit, and an optical pick-up unit for scanning a record carrier.
  • the record carrier can be either an optical disc (CD, DVD, BD) or a magneto-optical disc (MO).
  • CD compact disc
  • DVD digital versatile disc
  • BD blue-ray disc
  • CDs are low density information storage media
  • DVDs are high density information storage media
  • BD are the latest development of record carriers, allowing an ultra-high density of stored information.
  • the scanning which means the reading and writing of information on a record carrier by a spot of a radiation beam
  • the optical pick-up unit comprises a radiation source, in particular a semiconductor laser, emitting a radiation beam which scans (read and/or write) the information of the record carrier, whereby the wavelength of the radiation source is adapted to the information storage density being required for low density, high density and ultra high density record carriers.
  • the laser wavelength ⁇ is decreased and the numerical aperture of the objective lens is increased.
  • Scanning of CDs, DVDs and BDs requires radiation sources with different wavelengths.
  • the numerical aperture NA is for CD 0.45, for DVD 0.6 and for BD 0.85.
  • Several companies have developed optical recording systems that are able to scan as well CD-s, DVD-s and BD- s in the optical player.
  • Optical players that can read and write both DVD and BD-s are known as well as optical players that can read and/or write all three types of record carriers (CD, DVD and BD).
  • CD, DVD and BD optical players that can read and/or write all three types of record carriers
  • an optical pick-up is described, comprising lasers of different wavelengths as well as a plurality of objective lenses, each compatible with the family of optical record carriers.
  • Optical aberrations in the radiation beam on the record carrier due to a tilt of the objective lens and/or of the record carrier are more severe in an optical information storage system that operates with different record carriers than in an optical player being suitable only for one type of record carriers. This is due to the design of an information recording surface of the record carrier, in particular different spacing of the tracks and the size of the information carrying pits and due to the increased NA (numerical aperture), decreased wavelength in combination with the thickness of the cover layer on the disk.
  • the whole optical pick-up unit including the objective lens is moved additionally.
  • At least one of the optical branches comprises an optical component that is movable for correcting an optical aberrations occurring in the radiation beam.
  • the advantage of this optical pick-up unit according to the present invention is that the correction of the optical aberrations is performed in at least one of the optical branches. Additionally, the correction is performed by moving only one optical component, which is easier to perform. This is preferably an adjustment which is performed only once during the assembly of the scanning device/light path. This method avoids mechanically movable elements that are complicated and expensive.
  • a further advantage of the optical pick-up unit according to the present invention is that the correction of the optical aberrations can be arranged separately in every of the optical branches and adapted to the different types of record carriers of the optical pick-up unit. This leads to a further possibility of optimization of the scanning quality of the recorded information. It is further advantageous that due to the arrangement of the correction of optical aberration in at least one of the optical branches, the light can propagate along a common optical path that can comprise other optical components, for instance, a detection element which is part of the optical pick-up unit.
  • the working principal of the optical pick-up unit is described shortly in the following.
  • the radiation beam emitted from a first radiation source propagates along a first optical branch in which the optical component for correction is arranged.
  • the radiation beam After having passed a first optical path the radiation beam is directed into a common optical path of the optical pick-up unit, the radiation beam is then directed onto an reflecting element which directs the radiation beam onto an objective lens which focus the radiation beam onto a information recording surface of the record carrier.
  • the radiation beam is then reflected from the information recording surface of the record carrier and propagates along the common optical path of the optical pick-up unit onto a detection unit, which detects the radiation beam.
  • the detection element detects also the deviation from an ideal position of the radiation beam. It is clear from this description of the working principal that most of the optical elements, such as, the detection element, the objective lens and the reflecting element are disposed only one time in the optical pick-up unit, because they are part of the common optical path. This allows a cheap optical pick-up unit.
  • the optical component comprises a precollimating component, having a central lens axis.
  • the collimating component for correcting an optical aberration has collimating functions as well as the task to transform a radiation beam from radiation source, preferably a semi-conductor laser into a parallel radiation beam, which can then pass other optical elements and be directed and converged by the objective lens towards the record carrier to form a light spot onto a pit train on a track of the information recording surface of the record carrier.
  • Light reflected from the record carrier is converged by the objective lens and directed by an optical element to a detector.
  • the detector contains several segments in order to generate for instance a focus error signal and radial tracking signals.
  • the actuator moves the objective lens along the optical axis on response of the focus error signal in order to keep the spot on disk in focus.
  • the tracks on disk are followed by means of the radial movement on the actuator (fine tracking) and the radial movement of the whole housing of the light path (long range tracking).
  • the optical component is a collimating or pre- collimating component with a central lens axis.
  • the central lens axis is displaced with respect to the optical axis of the common optical path. Therefore, advantageously, both the objective lens and the collimating component can be moved according to the focus error signal and according to the quality of the focused radiation beam on the record carrier.
  • the optical component is arranged between the radiation source in the at least one optical branch and an optical element directing the radiation beam on the common optical path.
  • the central lens axis of the optical component is displaced against the optical axis of the common optical path.
  • the displacement of the central lens axis of the optical component causes, intentionally additional to the aberrations caused by the tilt of the objective lens or the record carrier, optical aberrations in at least one branch of the optical pick-up unit.
  • This intentionally caused optical aberration is intended to compensate the optical aberration caused by the tilt in the objective lens or are tilt of the record carrier. This results in a correction of the radiation beam on the information recording surface of the record carrier and therefore a better scanning quality of the record carrier is obtained.
  • the optical component is displaced by a tangential shift ⁇ , resulting in a shift of ⁇ in the central lens axis with respect to the optical axis of the common optical path.
  • This shift is preferably an adjustment which is performed only once during the assembly of the scanning device.
  • the optical component is displaced by rotation of the central length axis around one of the nodal points of the optical component.
  • the rotation around one of the nodal points of the optical component has the advantage that the image of the radiation source will not be shifted with respect to the optical axis of the common optical path.
  • the radiation source is additionally displaced by an amount that is related to the shift ⁇ of the central lens axis of the collimating optical component.
  • the shift of the laser has a fixed amount of (m-l) ⁇ .
  • the shift of the radiation beam is (m- 1 ) ⁇
  • the image of the laser will remain in the same place when the lens is shifted with a distance ⁇ with respect to the optical axis of the common optical path.
  • the quantity m is a magnification of the optical component. If this condition is fulfilled the spot of the radiation beam is kept centered on the detector, even if the central lens axis of the optical component is shifted, during the adjustment procedure when assembling the scanning device/light path.
  • one of the at least two optical branches comprises a radiation source for scanning an ultra-high density optical record carrier.
  • the optical pick-up unit for scanning an ultra-high density optical record carrier is extremely sensitive for optical aberrations, because of the very narrow tolerances caused by a very small distance of the pits and a shorter length of the pits due to the ultra-high density of the stored information. Therefore the correction of optical aberrations is extremely important in an optical pick-up unit that is suitable for scanning ultra-high density record carriers and low-density record carriers.
  • the optical pick-up unit comprises these at least three optical branches.
  • Three optical branches allow the scanning of three different types of record carriers, for instance the scanning of low density record carriers (CDs), high density record carriers (DVDs) or/and ultra high density record carriers (BDs) or also the scanning of magneto-optical record carriers (MO) with the same optical player.
  • CDs low density record carriers
  • DVDs high density record carriers
  • BDs ultra high density record carriers
  • MO magneto-optical record carriers
  • optical player with a drive unit and an optical pick-up unit according to the invention.
  • the correction of optical aberration in the optical pick-up unit used in an optical player allows that the optical player is able to scan different types of record carriers with a good scanning quality. This is because the optical aberration caused by a tilt of the record carrier or an unintentionally tilt of the objective lens or unwanted coma generated in the light path can be corrected in at least one of the optical branches by moving the optical component in this optical branch. Therefore the correction can be adapted to the requirements of the optical branch specifically and the tolerances that are used/required in this optical branch can be considered.
  • the object is also achieved by a method for correction of optical aberrations in an optical pick-up unit used in a multi-disc system, wherein a first type of record carriers and at least a second type of record carriers are used, the second type of record carriers having an information density different from an information density of the first type of record carriers, comprising at least two optical branches, a first optical branch having a first radiation source emitting a first radiation beam with the first wavelength, which first radiation beam propagates along a first optical path, and a second optical branch having a second radiation source emitting a second radiation beam with a second wavelength, which second radiation beam propagates along a second optical path, the first and the second radiation beam having different wavelengths and the first and the second optical paths being different and the first and the second radiation beam propagating - after having passed the first and the second optical paths - along a common optical path with an objective lens for focusing the first radiation beam or the second radiation beam at the record carrier by generating an optical aberration by moving an optical component in at least one of the optical branches.
  • the generated optical aberration is a coma.
  • the tilt of an objective lens or the tilt of the record carrier causes a coma as optical aberration. Therefore the intentionally caused coma in at least one of the optical branches advantageously corrects the coma caused by the tilt of the objective lens or the tilt of the record carrier.
  • the optical aberration is generated by displacing a optical component having a central lens axis by a tangential shift ⁇ .
  • This shift ⁇ is preferably an adjustment which is performed only once during the assembly of the scanning device.
  • the radiation source of the optical pick-up unit is additionally displaced by an amount of (m-l) ⁇ wherein m is a magnification of the optical component.
  • the radiation source is important to keep the spot of the radiation beam centered on a detector being arranged in the common optical path of the optical pick-up unit.
  • the central lens axis of the optical component is displaced against the optical axis of the common optical path by rotation of the optical component around one of the nodal points of the optical component.
  • the image of the radiation source will not shifted with respect to the optical axis of the common optical path.
  • Fig. 1 is a schematic view of the optical structure of an optical pick-up unit with three scanning branches for different optical record carriers;
  • Fig. 2 is a schematic view of a light pass configuration for CD, DVD and BD optical record carriers according to the present invention
  • Fig. 3 is a schematic view of a record carrier tilted with respect to an exit surface of an objective lens
  • Fig. 4 is an illustration of a jitter caused by optical aberrations due to a disc tilt
  • Fig. 5 is a schematic view of a pre-collimating component with a shifted central lens axis with respect to a common optical axis of the OPU;
  • Fig. 6 is a schematic view of a pre-collimating component, showing a rotation of the central lens axis.
  • information storage media are called record carriers.
  • record carriers For a low density record carrier such as a compact disc the abbreviation CD is used, for a high density record carrier the abbreviation DVD is used and for ultra high density record carrier the abbreviation BD is used. This includes both only read and/or read and write record carriers.
  • Fig. 1 shows a schematic view of an optical pick-up unit (OPU) 101, of the prior art, taken from US 2004/0114491 Al which is designed such as to be comfortable with various types of record carriers with different recording density, like CD, DVDs and BDs.
  • the OPU 101 comprises three branches 103, 105 and 107, each of the branches 103, 105, 107 is being suitable for another optical storage media. Please note that in the figure the record carrier is not depicted.
  • Each of the branches 103, 105 and 107 comprises an optical unit 109, 111 and 113, respectively.
  • the key parts of the optical units 109, 111 and 113 are radiation sources emitting laser light (in the following called radiation beams) with different wavelengths.
  • Radiation source 115 in the optical unit 109 is shown in place of the other radiation light sources.
  • the radiation beams of optical branches 105, 107 and of optical branch 103 are focused individually by a first objective lens 117 and a second objective lens 119 and are focused incident upon the record carrier (not shown).
  • Objective lens 117 and objective lens 119 are mounted on an actuator 121 of the optical units 109, 111 and 113.
  • the first and second objective lens 117 and 119 focus incident radiation beams so that the incident light beams are focused as optical spots on a recording surface of the record carrier (not shown).
  • the actuator 121 drives the first and the second objective lens 117 and 119 in a focusing and/or tracking direction.
  • the path of radiation beams emitted from the optical units are changed by reflection mirrors 123 and 125 so that the emitted beams are incident upon the first and second objective lenses 117 and 119.
  • the radiation beams emitted from the optical units 109, 111 and 113 may be directed incident upon the first and second objective lens 117 and 119 without the inclusion of the reflection mirrors 123 and 125.
  • the optical unit 111 comprises a light path changer 127.
  • collimators 129, 131 and 133 In the optical light path of all three branches 103, 105, 107 there are also collimators 129, 131 and 133 arranged.
  • the light path changer 127 is disposed between the second optical unit 111 and the second optical lens 119.
  • the first collimating lens 129 is disposed between the first optical unit 109 and the reflection mirror 123.
  • the second collimating lens 133 is disposed between the second optical unit 111 and the first light path changer 127.
  • the third collimating lens 131 is disposed between the third optical unit 113 and the first light path changer 127.
  • the optical unit 109 is described as having the radiation source, which is a laser with a short wavelength like a blue violet laser with a wavelength of 405 nm, the second optical unit 111 is described having a red laser with a wavelength of 650 nm and a third optical unit 113 is described comprising a near infrared laser suitable for CDs with a wavelength of 780 nm. Further details can be taken from this patent application publication and will not described here, because it does not belong to the present invention.
  • the radiation source which is a laser with a short wavelength like a blue violet laser with a wavelength of 405 nm
  • the second optical unit 111 is described having a red laser with a wavelength of 650 nm
  • a third optical unit 113 is described comprising a near infrared laser suitable for CDs with a wavelength of 780 nm.
  • this optical pick-up unit is designed for use in the multi disc system being able to scan three type of record carriers, wherein the information density of the three type of record carriers are different from each other.
  • the optical pick-up unit comprises two optical branches, a first optical branch having a first radiation source emitting a first radiation beam with a first wavelength, which first radiation beam propagates along a first optical path, and a second optical branch having a second radiation source emitting a second radiation beam with a second wavelength, which second radiation beam propagates along a second optical path.
  • the wavelengths of the two radiation beams emitted by the two radiation sources are different from each other as well as the two optical paths.
  • the two radiation beams are directed to a common optical path including the objective lens 119.
  • the third optical branch comprises a third radiation source emitting a third radiation beam having a third wavelength.
  • the third wavelength of the third radiation beam is different from the wavelength of the first and the second radiation beam.
  • the third radiation beam does not use the common path of first and second radiation beams and also comprises an additional objective lens 117 to focus the radiation beam onto the record carrier. Nevertheless, both objective lenses 117 and 119 are mounted on a common actuator 121 and can be moved. Additionally it is described to move the whole optical pick-up unit to perform corrections of the optical aberrations caused by a tilt of one of the objective lenses 117 and/or 119 and/or the tilt of the record layer.
  • the actuator moves the objective lens along the optical axis on response of the focus error signal in order to keep the spot on disk in focus.
  • the tracks on disk are followed by means of the radial movement on the actuator (fine tracking) and the radial movement of the whole housing of the light path (long range tracking).
  • the tilt between lens and disk can be corrected dynamically in one direction, by means of a tilt generated by the actuator.
  • Fig. 2 shows an schematic view of an optical pick-up unit 1 (OPU) of the present invention.
  • the optical pick-up unit shown in Fig. 2 is an example for an embodiment of an optical pick-up unit 1 to be used in an optical player (not shown) suitable for scanning record carriers with different information density.
  • the shown optical pick-up unit is designed to scan three different types of record carriers, in particular a record carrier with low information density, a record carrier with high information density and a record carrier with ultra-high information density. It is understood that this embodiment is only an example of multi disc system of an optical player and does not limit the present invention.
  • a light path configuration with three optical branches 3, 5 and 7 is shown, whereby branch 3 show the DVD branch, branch 5 the BD branch and branch 7 the CD branch.
  • recording branch 37 including a set folding mirror- ⁇ /4plate-disc and the objective lens 73 as well as the record carrier 35 should be rotated by 90° into a plane perpendicular to the surface of the paper. That is why in the optical pick-up unit 1 of Fig. 2 the optical record carrier 35 can be seen, even if the record carrier 35 is not arranged in plane with the optical branches 3, 5, 7.
  • This branch is assigned as a disc-writing branch 37 in the following.
  • the branches 3, 5, 7 are assembled in principle in the same way, comprising a radiation source, a pre-collimator lens and a grating as well as a beam splitter for directing the radiation beam into a different optical path.
  • Branch 3 includes a radiation source 39 (e.g. being suitable for writing and reading DVD's with high information density), a pre-collimator lens 41, a grating 43 as well as a beam splitter 45.
  • a pre-collimator lens is a lens that changes the vergence of the radiation beam in order to increase the coupling efficiency of the laser.
  • the radiation beam after a pre-collimator is divergent and not parallel as holds for a collimator.
  • the pre-collimator 41 in branch 3 can be shifted either tangential or rotational as shown with arrows 47 and 49 respectively.
  • Branch 5 comprises a radiation source 51 e.g.
  • Branch 5 suitable for scanning (writing/reading) record carrier with ultrahigh information density, for example, a semiconductor laser emitting a radiation beam with a wavelength of about 405 nm.
  • Branch 5 further includes a lens 53 that has the function of a beam shaper, a grating 55 as well as the beam splitter 57.
  • the branch 5 is suitable for scanning an optical record carrier 35 with ultrahigh information density.
  • Branch 7 comprises a radiation source 59, a pre-collimator 61, a grating 63 as well as a beam splitter 65 and is designed as to scan CDs with low information density.
  • the radiation source 59 is preferably a laser with a wavelength of about 780 nm. In the following the function of the three branches 3, 5, 7 are described.
  • the radiation beams emitted by the radiation sources 39, 51 and 59 are transmitted by the components 41, 53 and 61 as well as the gratings 43, 55 and 63.
  • each laser beam is directed onto a common optical path 66.
  • the radiation beam independently from the radiation source that produces the radiation beam, prolongate along this common optical path towards the objective lens 73 and consequently be directed to and focused on the record carrier 35 (which can respectively be a DVD, BD or CD).
  • a mirror 67 is included as well as in front of the mirror 67 a collimator 69.
  • a quarter wave plate 71 and an objective lens 73 are arranged in the recording branch 37 .
  • a detector 75 detects the radiation beam that is reflected from the information recording surface 76 of the record carrier 35.
  • a lens 77 is arranged to adapt the optical quality of the radiation beam, for example by introducing astigmatism.
  • a radiation beam from one of the radiation sources 39, 51 or 59 which are preferably semiconductor lasers, is formed into a pre-collimated radiation beam by the collimators 41 or 53 or 61 respectively.
  • the radiation beam is traveling along an optical path 4, 6 or 8 respectively and passes through a polarizing beam splitter 45, 57 or 65, and is converged by an objective lens 73 towards an optical disc 35 to form a light spot (scanning spot) onto the information recording surface 76 of the record carrier 35.
  • Light reflected from the information recording surface 76 of the record carrier 35 is converged by the objective lens 73 and directed by the mirror 67 to the detecting lens 77 and is finally incidenting on the detector 75.
  • the invention is not limited to the use of the specific components such as, for example, beam splitters and mirrors.
  • the invention may also include other optical components being able to change the direction of the radiation beam.
  • the detector 75 may contain several segments in order to generate, for instance, a focus error signal and radial tracking signal.
  • An actuator (not shown) moves the objective lens along the optical axis in response to the focus error signal in order to keep the scanning spot on disk in focus.
  • the tracks on disk are followed by means of the radial movement of the actuator (fine tracking) and/or the radial movement of the whole housing of the light path (long range tracking).
  • the function of the optical pick-up unit 1 is described for one of the branches 3, 5 and 7 respectively as following in relation to Fig. 2.
  • Light reflected from the record carrier 35 is converged by the objective lens 73 and directed by the mirror 67 to a detecting lens 77.
  • the converged radiation beam transmitted by collimator lens 69 forms a spot image near the center of the light-receiving surface of photo detector 75.
  • the photo detector 75 serves as detection element for all three branches 3, 5 and 7.
  • the detection error signal can therefore detect an optical aberration like a coma.
  • Coma may be produced by tilted optical elements in the common optical path 66.
  • the objective lens 73 can cause coma as well as a record carrier 35.
  • the amount of coma (W 31 RMS) of a tilted record carrier being tilted by an angle of ⁇ can be given by the following formula:
  • W 31 RMS -*V -l) sin ⁇ * cos ⁇ ⁇ ⁇
  • d the thickness of the disc
  • n the refracting index of the record carrier
  • ⁇ the angle disc tilt
  • NA the numerical aperture of the objective lens 73.
  • the relation between the coma and the angle ⁇ is depicted in Fig. 3 showing the record carrier 35 and the objective lens 73 as well as the angle 79 indicated between a straight line 80 expressing an angle of 0° and being identical with the surface of a non-tilted record carrier 35.
  • the thickness 81 of the record carrier 35 can also be seen in Fig. 3.
  • the accuracy of the light spot on the information recording surface 76 of the record carrier 35 is influenced and with that the scanning quality of the high frequency signal.
  • the quality of the high frequency signal can be expressed in terms of jitter. Jitter may be understood as a timing error of the zero crossing of the high frequency signal.
  • the optical pickup unit 1 is properly aligned in radial as well as tangential direction.
  • This curve expressing the dependency of the jitter 83 from the tilt angle 79 of the record carrier is called a bathtub curve 84.
  • the position of the bathtub curves may be depicted as function of the angle ⁇ .
  • the bathtub curves 84 and 84' (dotted line) show an offset 85 as indicated. That means that bathtub curves 84 and 84' have an offset 85 of the point of jitter 83 being zero.
  • the offset 85 of the jitter curve can corrected, as shown in prior art optical pick-up units, by tilting the objective lens in the optical pick-up unit. If the coma occurs only in one of the branches 3, 5, 7 the jitter correction (by tilting the objective lens 73) is always a compromise and a point of minimum jitter will not be reached for all the branches of the optical pick-up unit 1.
  • the point of minimum jitter 83 for BD and DVD will usually not coincident as can be seen in Fig. 4b. Consequently the tilting of the objective lens cannot be done for both of the branches 3 and 5 being designed to scan the record carriers 35 (e.g. a BD or a DVD).
  • a bathtub correction of the prior art could result in a bad scanning performance for one of both record carriers, BD or DVD. Therefore, as shown in Fig. 2, the bathtub correction is performed in at least one of the optical branches 3, 5 or 7. As an example it is shown in Fig.
  • the optical pick-up unit 1 comprises an optical component 41, 53 or 61 suitable for bathtub correction.
  • the optical component 41, 53 and 61 is a pre-collimating component arranged between the radiation source and the grating.
  • This pre-collimating component may be movable or shiftable in a tangential direction (as indicated with arrow 47 for branch 3) or in a radial direction (as indicated with arrow 49 for branch 3).
  • the shift of the pre- collimating component 41 is performed by shifting the central optical axis 87 of the collimating component 41 with respect to the optical axis of the common optical path 66 of the optical pick-up unit 1.
  • the shift is of the amount ⁇ and the radiation source 39 is shifted by an amount (m-l) ⁇ the imaged spot of the radiation source 39 is kept centered on the detector 75.
  • the shift of the central lens axis 87 of the pre-collimating component 41 is shown in Fig. 5, wherein the central lens axis 87 is marked with the reference sign 87 and the optical axis of the pick-up is reference sign 88. The shift is indicated with a reference sign 89.
  • m is the magnification of the pre- collimating component 41. That means that the shift of the radiation source with respect to the optical axis is depending on the magnification m of the pre-collimating component 41.
  • a nodal point is a point on the optical axis and is constructed like the following: When both the incoming and the outcoming rays of the radiation beam are extended until they meet the optical axis, they meet in the nodal points.
  • the bathtub correction can be arranged in all of the three branches 3, 5 and 7 and that the bathtub correction is performed by a pre-collimating component in each of the branches 3, 5 and 7.
  • the pre-collimating component is then displaced either tangentially or radial or rotated in, preferably, one of the nodal points of the pre-collimating component. It is important for a correct bathtub correction that the spot of the radiation beam is not displaced on the detector 75 after a displacement or rotation of the pre-collimating component 41.
  • the embodiment shown in Fig. 2 is an example of an optical pick-up unit 1 including a bathtub correction and should be seen as an example that does not limit the invention.
  • the basic idea of the invention is that bathtub correction is arranged in at least one of the optical branches 3, 5 or 7 and can perform the bathtub correction individually for each branch when necessary.
  • the optical pick-up unit 1 comprises only one objective lens 73 that is common for all three optical branches 3, 5 and 7 and is arranged in front of the information recording surface 76 of the record carrier 35.
  • the system also comprises a single detector 75 in common that detects the radiation beam reflected from the information recording surface 76 of the record carrier 35 and is used for creating an error signal for the bathtub correction.
  • the shift, displacement or tilt of, for example, the pre-collimating component 41 in branch 3 may be adjusted during assembly in order to minimize the jitter when scanning a record carrier.
  • the means for displacing or tilting such a pre-collimating component are not discussed here in details. It can, for example, be done mechanically or electromechanically. It may also be possible to apply a device, such a micro mechanical device (for example using MEMS technology), that allow for a small shift or tilt of the component.

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Head (AREA)

Abstract

La présente invention se rapporte à une unité de détection optique conçue pour être utilisée dans un système à disques multiples, permettant d'explorer un premier type de supports d'enregistrements et au moins un deuxième type de supports d'enregistrements, le deuxième type de supports d'enregistrements ayant une densité d'informations différente de la densité d'informations du premier type de supports d'enregistrements, ladite unité de détection optique comprenant au moins deux branches optiques (3, 5, 7), une première branche optique (3) ayant une première source de rayonnement (39) émettant un premier faisceau de rayonnement d'une première longueur d'onde, ledit premier faisceau de rayonnement se propageant le long d'un premier chemin optique (4), et une deuxième branche optique (5, 7) ayant une deuxième source de rayonnement (51, 59) émettant un deuxième faisceau de rayonnement d'une deuxième longueur d'onde, ledit deuxième faisceau de rayonnement se propageant le long d'un deuxième chemin optique (6, 8), les première et deuxième longueurs d'onde et le premier et le deuxième chemin optique (4, 6, 8) étant différents et le premier et le deuxième faisceau de rayonnement se propageant - après être passés sur le premier et le deuxième chemin optique (4, 6, 8) - le long d'un chemin optique commun (66) comprenant un objectif (73) conçu pour focaliser le premier faisceau de rayonnement ou le deuxième faisceau de rayonnement au niveau du support d'enregistrements (35). L'unité de détection optique se caractérise en ce qu'au moins une des branches optiques (3, 5, 7) comporte un composant optique (41, 53, 61) qui peut se déplacer pour corriger une aberration optique dans le premier ou le deuxième faisceau de rayonnement.
PCT/IB2005/054000 2004-12-06 2005-12-01 Unite de detection optique concue pour etre utilisee dans un lecteur optique pour disques multiples et procede de correction des aberrations optiques dans une telle unite de detection optique WO2006061745A2 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
DE112005003102T DE112005003102T5 (de) 2004-12-06 2005-12-01 Optische Abtasteinheit zur Verwendung in einer optischen Mehrfachdisk-Abspieleinrichtung und Verfahren zum Korrigieren optischer Abweichungen in einer derartigen optischen Abtasteinheit
US11/792,275 US20080259770A1 (en) 2004-12-06 2005-12-01 Optical Pick-Up for Use in a Multi-Disc Optical Player and Method for Correcting Optical Aberrations in Such an Optical Pick-Up Unit

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP04106312.4 2004-12-06
EP04106312 2004-12-06

Publications (2)

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WO2006061745A2 true WO2006061745A2 (fr) 2006-06-15
WO2006061745A3 WO2006061745A3 (fr) 2006-09-14

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US (1) US20080259770A1 (fr)
DE (1) DE112005003102T5 (fr)
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JP3547038B2 (ja) * 1998-10-06 2004-07-28 パイオニア株式会社 光ピックアップ装置
US6423956B1 (en) * 2000-07-28 2002-07-23 Optical Biopsy Technologies Fiber-coupled, high-speed, integrated, angled-dual-axis confocal scanning microscopes employing vertical cross-section scanning
WO2003003360A1 (fr) * 2001-06-29 2003-01-09 Koninklijke Philips Electronics N.V. Dispositif de balayage optique
JP2004062918A (ja) * 2002-07-24 2004-02-26 Pioneer Electronic Corp チルトサーボ装置
JP2004145907A (ja) * 2002-08-30 2004-05-20 Konica Minolta Holdings Inc 光ピックアップ装置、集光光学素子及び補正素子
KR100911141B1 (ko) * 2002-09-03 2009-08-06 삼성전자주식회사 틸트에 따른 파면수차 보정 기능을 갖는 렌즈 및 광픽업
JP2004133958A (ja) * 2002-10-08 2004-04-30 Pioneer Electronic Corp 光ピックアップ装置
JP2004288346A (ja) * 2002-10-18 2004-10-14 Konica Minolta Holdings Inc 光ピックアップ装置用の光学素子、カップリングレンズ及び光ピックアップ装置
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JP5002118B2 (ja) * 2003-06-18 2012-08-15 コニカミノルタアドバンストレイヤー株式会社 光ピックアップ装置用の光学素子、及び光ピックアップ装置
JP2005158171A (ja) * 2003-11-27 2005-06-16 Pioneer Electronic Corp 光ピックアップ
JP2005166195A (ja) * 2003-12-04 2005-06-23 Canon Inc 光情報記録再生装置及び光情報記録再生方法
JP4419654B2 (ja) * 2004-04-02 2010-02-24 コニカミノルタオプト株式会社 光ピックアップ装置
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US20080259770A1 (en) 2008-10-23
WO2006061745A3 (fr) 2006-09-14
DE112005003102T5 (de) 2007-10-25
TW200638385A (en) 2006-11-01

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